The Epidemiology, Database Management, and Statistics (EDMS) Core will provide the central epidemiologic, data management and biostatistical resources for the projects and other Cores. The EDMS Core will participate in Core-to-Core acitvities by weekly meetings with the other Core leaders and the the program coordinator to review and discuss all data-related issues, including cohort follow-up and retention, data completeness, and data retrival. The Core has three components. Data generated by each of the other cores and research projects will be transferred to the Database Component for entry and storage in an integrated SIR/DBMS data management system designed to meet all the needs of the program project with respect to cleaning, organization and retrieval of data for planned analyses. The activities of the Database Component will be carried out on a networked system of computers especially configured for data management operations. The Epidemiology Component will provide expert consultation in epidemiolgic methods, hypothesis testing, and in the interpretation and presentation of research findings. It will provide guidance on methodological issues such as subject classification on risk factor, outcome and related variables, development of derived variables, matching, bias and confounding. These activities will be carried out by means of bi-weekly meetings with Core statisticians and individual project investigators on a rotating basis and by a monthly joint meeting of project investigators to review manuscripts in preparation. The Statistics Component will be responsible for the planning and implementation of all analyses conducted by investigators. Core Statisticans, in collaboration with the Clinical and Brain Imaging Cores, will provide common summary outcome measures related to cognitive and functional performance, and to brain imaging results and will employ a core set of strategies for the analysis of large prospective multivariable and multivariate longitudinal datasets that pose common problems for the projects. By centralizing data management, epidemiological and statistical oversight in the EDMS Core, we will ensure the consistency and facilitate interaction of the projects with respect to uniform definitions of variables, data summarization, choice of tests, model building and interpretation of study results.